|Origin:||questionner 'to question'|
a written set of questions which you give to a large number of people in order to collect information
fill in/fill out/complete a questionnaire (=answer all the questions in it)! Do not use questionnaire to mean 'a study in which many people are asked questions to find out their opinions or behaviour'. Use survey: We conducted a survey (NOT a questionnaire) to find out what students think about sport.
All staff were asked to fill in a questionnaire about their jobs.